If my father writes will( of grandfather property) on my name

The property inherited by your father from his father either by partition or any other mode of acquisition becomes your father's self acquired property, hence he has full rights to dispose them in any manner and in anyone's favor as per his will and wish.

Your sister cannot claim a share in it as a right.

Firstly you should open a different thread to seek opinion to your own problems, if you are joining the thread opened by other person then you should be a person responding to the query.

Now to your question:

The grandfather's property is not ancestral property in the hands of the son who inherited the same as his legal heir or successor in interest.

It becomes his self acquired property and gives him full rights to dispose it in any manner and to anyone of his choice.

The grandchildren cannot question or challenge the authority of thier father in this situation

I have analysed your query and would like you to know that Section 8 of Hindu Succession Act, 1956 provides the rule of succession in the case of Hindu male dying intestate, property shall devolve as:

(a)    Firstly, upon the heirs, being the relatives as specified in the class 1 of the schedule.

Now, class 1 heirs include sons, daughters, mother and widows who can claim property. In the case of multiple survivors each survivor will get one share each.

Section 10 provides rules for distribution of the property among the class 1 heirs:

Rule 3 – The heirs in the branch of pre-deceased son or daughter of the intestate shall take between them one share.

This provides that grandchildren do not have any birthright in the property of their grandfather unless their father is pre-deceased and grandfather dies intestate, then in that case the grandchildren can acquire their father’s share in the grandfather’s self-acquired property being one of the class-1 heirs.

In your case, since your father has inherited his share in your grandfather’s property, it will be considered as his self-acquired property, he has the right to prepare a will or gift the property to anyone he wishes, your sister does not have any right to object. However, if your father dies without making a will then the property will be distributed equally among his legal heirs.

Hope it helps you with your query.

Regards,

Parth Chawla

Dear Siddharth,
Thank you for your query! I am Aadil and I will try to answer your question.

The short answer to your question will be NO, your sister shall not have any claim towards her father’s property, provided said property is self-acquired.

The answer to your question depends on whether the said property is ancestral or self acquired. 
For a property to come under ancestral property in India, it must be one that has been passed on for four generations by the male ancestors, according to the Hindu Succession Act, 1956. It must not have been partitioned, sold, or divided during this time. If it was, the property will lose its ancestral status and shall now be treated as self-acquired property.
If your property is ancestral, then the two children (You and your Sister) shall have the claim for inheritance to said property, which means your sister has the right to go to court for the same.

Assuming that your property is not ancestral and is instead self-acquired, it is completely upon your father to choose who may inherit his property by including their name in his will. This right cannot be questioned by any of his children, including his daughter.
Even though your father only acquired this property upon the death of his intestate father (Your Grandfather), him being a legal heir to his father as per Section 8 of the Hindu Succession Act, 1956, gives him complete control over this property. His children shall have no claim over it unless he dies intestate or if their name was included in his will.

I hope this helps. Thank you for your time and patience!

Regards,
Aadil